1. Field of the Invention
The present invention relates to an image recording apparatus which displays are image represented by a video signal produced by an image reader or a computer on the screen of a CRT (cathode-ray tube) and then exposes a photosensitive recording medium to the screen of the CRT which serves as a light source.
2. Description of Related Art
An image recording apparatus employing a CRT as a light source to record an image displayed on the CRT on a photosensitive recording medium is known. One embodiment of such an apparatus is disclosed in U.S. Pat. No. 4,712,909. The image recording apparatus disclosed in the above U.S. Pat. is provided with a computer and an internal CRT for displaying an image produced by the computer. A photosensitive recording medium is exposed to the image displayed on the CRT to record the image on the photosensitive recording medium. The image produced by the computer is displayed also on an external CRT. The operator is able to recognize the image to be recorded on the photosensitive recording medium by monitoring the image displayed on the external CRT.
It is desirable that the image recording apparatus is capable of receiving video signals from an external device to improve the utility of the image recording apparatus employing the CRT; that is, it is desirable that the image recording apparatus is capable of being connected to an optional external image producing apparatus, such as a computer or an image reader, and capable of recording an image represented by a video signal produced by the external image producing apparatus. In such a case, the operator is able to recognize the image to be recorded by monitoring the image displayed on the CRT of the external image producing apparatus.
The CRT included in a host computer as the external image producing apparatus connected to the image recording apparatus and operated by the operator for image production has an aspect ratio which is specific to the maker or the type of CRT of the host computer, while the internal CRT which serves as a light source of the conventional image recording apparatus, such as in the above-referenced U.S. Pat. No. 4,712,909, has a fixed aspect ratio. Accordingly, it has been impossible to adjust the aspect ratio of the internal CRT to that of the CRT of the host computer. When a video signal produced by the host computer corresponding to an image displayed on the external CRT attached to the host computer is displayed on an internal CRT which has an aspect ratio different from that of the external CRT, the following problems arise:
For example, when a video signal representing a circular pattern P1 as shown in FIG. 2(a) produced by the host computer is applied to the image recording apparatus, a vertically elongate, elliptical, pattern P2 as shown in FIG. 2(b) or a horizontally elongate, elliptical, pattern P3 as shown in FIG. 2(c) is displayed on the screen of the internal CRT serving as a light source. That is, an image recorded by the image recording apparatus is different from the image displayed on the screen of the CRT of the host computer.